Thermic balance or radiometer.



R. D. PARKER. THERMIG BALANCE OR RADIOMETEB.

APPLICATION FILED JULY 31, 1912.

1,099,199, PatentedJune9,'1914.

VMZWES%W W 7W WMMM ATTO R N EY UNITED STATES PATENTOFFICE.

aanznmorm DRAKE Panxnn, or; ANN ARBOR, MICHIGAN.

This invention relates to thermic balancesor radiometers and has for itsobject animproved instrument capable of detectingl the presence of-abody by its sensitiveness to the ethereal radiation produced by thatbody and consists in improvements in radiometers as well as in a noveladaptation thereof to produce an instrument sensitive only to the energyradiated by bodies, and also rugged enough to be used asa commercialinstrument with particular reference to its use as a detector of thepresence of bold bodies, as icebergs. I'accomplish this and the other.objects by the apparatus hereinafter described:

In the drawings: Figure l, is a. diagram of the electrical features ofthe instrument. Fig. 2, is a section of a arabolic mirror that is usedto focus the radiant ener upon a certain part of the instrument. 1g. 3,is a section of the receiving tube which is" affect ed by the radiantenergy.

B is .a parabolic mlrror arranged to focus the radiation at a givenpoint or place. -'This place and the fOOllSlIlilS shown by the dot tedlines in Fig. 2. T e rays are focused on a portion of a tube which-projects in the axis of and through the rear of the mirror, whichportion is characterized as c,

Referring to Fig. 3, it will be seen that o and 6 indicate coils bothbeing covered by a mica cylinder 10. a and d. each indicate coils whichlie under a silvered glass. cylin der 11 which reflects the etherealradiation and prevents the conduction ,of the ethereal radiation to thecoils. 1 Other material may be used to reflect such radiation, as, forinstance polishedmetal. Tis a sleeve made of non-conducting material forheat and is adapted to pass over and cover more or less of the silveredglass cylinder 11 and the mica cylinder 10. By sliding it along thesurface of those cylinders it extends through the Specification ofLetters Patent. Application filed July 31, 191i. Seria1No. 712,394.

. THERMIG BALANCE B BADIOMETER.

Patent ed June 9, 1914.

mirror B encircling the casing 11 and may be,-1f necessary, held inadjustment by an ordinary set screw or any other convenient:

means. In Fig. 3 of the drawings the cylinder is shown by solid lines,and the extent to which it may he slid along and cover the silveredglass cylinder 11 is shown by the dotted lines. l/Vhile I prefer to usethe sleeve in this manner, it is not strictly essential to the operationof the device as it is expected that the silvered glass cylinder 11 willeffectually reflect the radiant heat. The mica cylinder acts as aconductor ofthe radiation to coils 0, Z) but any other equivalentsubstance, such as rock salt, could be used to accomplish this function.Each of' these coils a, b, 0, and d is apart of the well knownWheatstones bridge which is illustrated diagrammatically in Fig. 1. Itis, therefore, obvious that radiation affects the coils sand I) to agreater degree than coils a and (Z.

By comparing Figs. 1 and 3, it will be observed that the. conductor 1,in each figure, leads from the junction of windings a and b and that theconductor 2 leads from the junction of windings o and d. The bridge awire 3, in each figure, leads from the junctioii of b and d, and thebridge wire 4, in each figure, leads from the junction of coils a and c.The bridge wires lead to a galvanometer G which indicates anydifferences in potential in 21-well known way that needs no explanation.Y

E, is a source of electromotive force. R,

is a rheostat for controlling the flow of current through the circuitand A is an amineter for indicating the magnitude of the current-flow.The object of this electromotive force is twofold, first, to supplyenergy to the galvanometer and secondly to heat the coils a, b, c, d bymeans of the electric. currentto a proper constant degree aboveatmospheric temperature.

Since the transfer of energy between two bodies by radiation depends onthe difierence of the fourth powers. of their absolute temperatures,warming the radiating port-ion of the bridge, to and maintaining itat amoderate temperature. above and independent of atmospheric conditionswill enormously improveits sensitiveness and reliability for thedetection of colder bodies.

It is well understood that the resistance of.

conductors changes with the temperature,

hence'when radiation strikes the mica lO,

is conducted through that covering, changes the temperature of the coilsb and c and changes the electrical resistance of windings b and 0.Therefore since these coils are ar- 5 ranged with respect to thecomplete Wheatstones bridge as indicated in the diagram-v matic figurethere is a change in the current flowing through the galvanometer G,irre spective of the predetermined initial temperm ature of the coils.The material of which the coils or windings are made may have a plus orminus temperature coeflicient, which 'coeflicient should be as large aspossible. It is evident that a material with a minus .15 coeflicient'isthe more suitable for great sensitiveness, once stability is secured,since the heating effect of the current in the coil then aids in causinga change of potential to act on the galvanometer.

In the Wheatstone bridge'as represented' in Fig. 1, the electromotiveforce impressed on the galvanometer is the difference between the fallof potential over the resistance 6 and the fall of potential over theresistance a. A change in the electromotive force impressed on thegalvanometer therefore arises from a change of resistance, or of eurrent, or of both in one or both of these i st. ances. With directcurrents the fall 0 potential over a resistance is equal to the productof the resistance by the current through the resistance. In order toobtain a maximum change in electromotive force acting on thegalvanometer due to a given change in resistance, the. current should beas independent of the resistance changes as possible and as large as isconsistent with the size of conductor employed and the amount .ofheating allowable. Since the resistance of a conductor at anytemperature ,is given by the expression Rt=Ro(1iBt) it is evident that achange of resistance arising from a change of temperature from v t to t,is equal to the product BRo(tt') and R0 should be a large quantity inorder for the instrument to be sensitive to small changes oftemperature. The a two coils b and c are each made sensitive toradiation as hereinbefore described and placed at such- Resistance of bResistance of a Resistance of'd' Resistance of c .it is evident that ifthe resistances ofb and '0 are, both increased the ratios become moreunequal than if one alone isincreased, hence the changes inelectromotiveforce will. be

greater and the instrument will be more sensitive, other factors beingthe same.

From the above it is evident that the loss of absorption of radiantenergy by the sensitive radiating portions of the bridge merely controlsthe amount of current or energy supplied to the galvanometer circuit,the

electromotive forceEbeing largegnough to operate this galvanometerthough thet'em perature changes are extremely slight.

It is evident that the instrument may be so designed that under normalconditions a current will flow through the bridge wires 3 and 4, asshown by the arrows. This current would cause the pointer P to turn werenot this tendency overcome by a light spring in which causes the pointerto take a neutral position under normal conditions. This provision ismade so that if at any time the current in the circuit fails, theposition of the pointer will change and indicate this failure which maybe remedied before the instrument has met with an occasion where it iscalled upon to register the presence of such objects as it was designedto indicate.

In the apparatus I have shown normally closed electrical circuits 14 and18, each in cluding an electric lamp and a magnetically operated device.These circuits are opened by the movement in either direction of the armor pointer P as hereinafter described. It is evident that any type orkind of indicating device working on the principle of cessationofcurrent flow may here be employed.

If there is any small change in the radiation, it is quickly detected byreason of the focusing of the radiation upon the mica 10 and itsconduction through to the coils 0 and Z) where the energy is absorbed bytheir blackened surfaces and their reslstances thereby'changed. Anincrease of temperature, say, causes more resistance, if the temperaturecoefiicient is positive, in the arms 0 and b and ,hence less currentflows through the bridge wires 3 and 4 in the direction of the arrow,and the galvanometer moves to the right. If it moves as far as theterminals 16 and 17, it opens the circuit 18 which deenergizes themagnet 19 and drops armature 22, and extinguishes the light 24, oroperates any other signal. This immediately shows the presence of somehotter body. If, instead of the temperature of c and b increasing, thetemperature decreases, then their conductivity is improved, 'withpositive temperature coefficient, and a somewhat higher potentialdifference will be established between 3 and 4 and more current willflow through the galvanometer and the pointer will swing to the left. Ifit swings far enough, it willstrike the terminals 12 and 13 and open thecircuit 14 extinguishing the in- "candescent light 15 or actuating anyother I signal depending on a CBSSRtIOII Of the cur rent that may beused in its place or in addition to it. This will show the presence ofsome colder object.

It will be understood that by fixing the position of the parabolicmirror all objects except those directly within the opening of themirror may be excluded from afiecting the instrument. .Therefore inusing the device upon boats, it ma be arranged to be faced 'ous supplyof heat energy by conduction,

in the direction travel of the boat so that only radiant bodies asicebergs that are in or near the path of the ship will affect it. Ofcourse it may be arranged to be swung into any position or direction. Itis not susceptible to mere atmospheric changes since all four windingsare of the same material substantially equal in resistance, and thethickness of the protective coatings is so designed that the coils willcool or warm at the same rate due to loss or increase ofheat byconduction and correction of which adjustment is obtained by means ofthe sleeve T.

In order to maintain a constant temperature of the bridge coils, acontroller U for the rheostat may if desired be inserted in the circuit,but such constant temperature is not strictly essential to the operationof the device. As these controlling devices are not new it isunnecessary to describe them surrounding circumstances; for instance,the

indicating device might be placed, say, in a pilot house at somedistance from the refiector and coils, or they might even be carried tothe engine room, or even duplicated in each place though on the samellnes and affected by the same instrument without departing from theinvention.

It is obvious ,that .the details of-the ar-' rangement I have shown andescribed may be widely varied without departing from my invention and Ido not wish to be confined to those and their exact structure.

WVhat I claim is 1. In combination, four resistances for an electriccurrent arranged in-pairs of two resistances each, two such coupledresistances,

adapted to be affected by radiant heat,

I means for concentrating radiant heat thereon, theremaining two coupledresistances being screened therefrom, means for suchscfeening'substantially as described, means for electrically connectingthe coupled resistances whereby the changes! in electroas described. v r2. The combination and arrangement of two pairs of substantially equalresistances as 'cb and a,'d, means 'for subjecting each pair to asubstantially equal and simultanemeans for subjecting one of the pairsto radiant heat energy, and means for barring the other pair therefrom.

3. The combination and arrangement of two pairs of substantially equalresistances as cb and a0Z, means for subjecting each pair to asubstantially equal and simultaneous'supply of heat energy byconduction, .meansfor subjecting one of the pairs to radiant heatenergy, means for. barring the other pair therefrom, a source ofelectrical energy connected to the pairs so as to develop a currenttherethrough, and an indicator in the path of said current.

4. The combination and arrangement of two pairs of substantially equalresistances as 0--b and H, means for affecting them equally andsimultaneously by conduction of heat energy, means for subjecting one ofsaid pairs'to radiant heat. energy, means for barring the other pairtherefrom, a source of electrical energy so connected to the pairs as todevelop a current therethrough, and an indicator adapted to show-changes in resistance in one, pair caused by theheat radiationoperating on one of. the.

resistance pairs.

5. The combination and arrangement of 6. The combination and arrangementof two pairs of four resistances having a nega tive temperaturecoefficient of resistivity, means for affecting both pairs substantiallyequally and simultaneously by heat energy delivered by conduction, meansfor subjecting one of the pairs to radiant energy,

a source of electrical energy to supply a current to heat both pairs ofresistances, and an indicator operated by such electrical energy to showchanges in resistances.

.,7. In a device for indicating changes in radiant heat energy, thecombination of a casing carrying two pairs of substantially equatelectrical resistances, a parabolic mirror encircling said casing andarranged to reflect radiant heat energy upon one of said v pairs ofresistances, a sliding sleeve adapted means for barring the other pairtherefrom,

to screen the other of said electrical resist- In testimony whereof, Isign this specifiances therefrom, means for furnishing a cation iii thepresence of twowitnesses.

constant current through said resistances in parallel, and an indicatorto show changes \RA-LZEMOND DRAKE PARKER inresistances due to increaseor decrease of Witnesses:

temperature in one of the pairs thereof, sub- VIRGINIA C. SPRATT,

stantially as described. I ELLIOTT J. STODDARD.

